They used to call it the train of shame, this last train out of town. Tonight it has already shed most of its drunks and Julian rests his arms across his knees, a college library book on the table before him and a scruffy paperback of Yeats sticking out of his pocket. The moon keeps pace as the train hurtles west and the air is heavy with the perfumed-garden-of-hell of the toilet. He ignores both books and the big old moon and twirling a matchstick between his teeth rests his head to the window thinking only of Julia.

He missed all his connections because of her – she should never have come to see him off dressed like that – her presence as consuming and chemical as the first time he saw her. Falling in love: instant and soaring and experienced in places less poetic than the heart, as those who have fallen know. Yes, his heart lurched. But did his kidneys? His stomach? His gall bladder? His bowel? The shape of his love was littered with organs. There wasn't a part of him that didn't leap the instant his eyes first alighted on Julia.

It was as though she had sprung fully formed from his forehead: Julia standing on the crest of the Downs with three counties falling away behind her and her long hair flying. Just moments before he had been dreaming her up, this very woman, as he climbed the chalk path, a little breathless from the gin-soaked night before. He'd summoned her from the depths of his hangover. Ta-da! Wished her into being. She was everything he desired: her stance, her attitude, everything, right down to the muscular brown calves that emerged from her cut-off blue jeans.

The wind came in chaotic gusts that bowled him along the grassy ridge. She was walking backwards into the wind, staring towards the trees, and she didn't notice him coming until he was close enough to make her jump.

"Hi," he called out and as she turned with startled brows he saw that her face was just as he'd dreamed it, neatly featured and out of a tan skin and dark lashes her eyes an astonishing Siamese cat blue.

"Whoa, it's blowy," he said, amazed he could speak. She nodded and gestured: "Look out," and as she raised her left arm he noticed her leather gauntlet and he followed her eyes skyward to the bird that was falling, turning and turning, like a heart that had leapt free. It fell, this falcon, and he was transfixed, his was the raptor's gaze; he was hurling himself straight at her from the heavens. The beat of its wings was the beat of his blood as it landed on her outstretched arm, claiming her, snatching her wrist with its yellow and black feet, jealously shielding the meat that she gave him beneath a mantle of wing and tail feathers. Julian realised that he was out of breath.

She laughed at his astonishment. "Manners, Lucifer," she said as it tore the meat from her. "He's a Harris hawk," she said when he asked. The hawk regarded her with psychopathic eyes.

"Don't be so greedy you rude thing," she scolded, and Julian noticed her shirt billowing, the sheen of her skin. "And if you don't hurry up I'll be late for work." She held a second morsel, pink and stringy, in the gauntlet.

A leather tassel hung from her wrist: the way the hawk stripped the meat made it jerk about and swing.

"What's that you're feeding him?"

"Don't ask," she wrinkled her nose in a way that made his heart tender. Perhaps he was dreaming? Another mischievous gust revealed a leather belt and above it the momentary distraction of a long narrow stomach, smooth as new brown paper.

"All the way up here to fly him, and it's perfect this wind, but he hasn't caught a thing to eat for himself this morning."

He listened for clues to her exotic looks in her accent but found none. She pulled a face at the hawk and it took the cue to fly from her, imperious feathers rustled, reeling away to the trees.

"Off we go again," she said and Julian watched the swing of her walk as she headed for the copse, the loose folds of white shirt gathering at her waist and the hawk circling overhead. From her belt hung a pouch from which she'd taken the bits of meat. The bag bounced against her hip, the gauntlet was comically large at the end of her slender arm.

The hawk landed in a tree and Julian found he was holding his breath, arms stretched out at his sides, waiting for it to fly to her, his every muscle tensed. But Julia marched on, and started to lollop and then to jog. As she reached the corner it hit him as suddenly as waking to the click of fingers.

He panicked, unable to think of a thing to shout. He patted his pockets impotently. All he had on him was the key to his bike lock and a wrap of tobacco. Was there nothing he could pretend she'd lost? He watched her disappear around the edge of the trees, hands helplessly hanging at his sides. He ran to the copse, across mounds of grass that left him stumbling, but there was no sign of her. Time seemed to slow until he felt like a sleepwalker wending through the undergrowth, brambles snatching, unable to find his way through the trees. The wind dropped and the branches stilled. He stopped, leaned against a tree trunk; through the leaves he could see only crows circling, their callous shouts echoing around the Downs.

For days his heart struggled, as did his stomach and complexion, aggravated by a listless diet of hangovers and poetry at his digs and nights working his summer holiday shifts at the Crown among the insolent drunks, pulling pints and mopping slops. At some point his mother called but that was all.

On the ninth day he roused himself and cycled to Swallow Street, where he chained his bike to the lamppost by the head shop, nodded to Pete the hippie, and headed for the antiques and bric-a-brac. The first thing to catch his eye was a collection of brass padlocks, Victorian, earlier some, polished to a shine: he felt like a magpie he liked them so much, one in particular shaped like a heart. These shops were not priced for students but that couldn't be helped. Some impious spirit had made him lie to his mother when she phoned: "I've found an incredible present for you, I can't wait for you to see it …"

He wandered from the padlocks to check that his favourite object was still on display at Geldings Antique Shop. And there it was, flamboyant in the window: a wind-up mahogany gramophone with gleaming trumpet, like a strumpet kicking her skirts.

Just seeing it, waiting there in full bloom, restored his heart and he gave his knuckles a little crack to prove it. He'd been bad-tempered all week because of that girl and was beginning to wish she'd remained in his dreams. He'd been ungracious when his mother called: Firdaws? Her birthday? The river?

"Seeing you will be better than any fancy present," she had said. "I miss you … And swimming. You're the only person who'll still take the plunge."

"We'll cook fish in the tin bucket …" she promised and he tried not to hear relief as well as delight in her voice when he told her that he wouldn't dream of missing it. "And all the usual things."

He'd stopped listening to her for a while, and thought instead of the girl with the hawk.

"I'll be there," he sounded terse to his own ears. Sometimes he felt he was offering her scraps from his table.

They talked some more of Firdaws, of the doomed beauty of the cockerels, strutting around the orchard like little emperors. "Maybe we should take them to the woods and leave them there. Care in the community," she said, making him laugh. "They'll have to go soon. Some of my poor girls look oven ready they've been so amorously plucked."

There were plump artichokes ready for him in the garden and trees heavy with plums. He thought of the soft roses and the river flowing and the hammock between the crab apple trees in a landscape as familiar to him as the face of his mother.

On her birthday each year his mother Jena swam a mile or so down the river. She dived from high above the water, from the bank where they picnicked on a day that the sun wouldn't dare not to shine. The river was wide there, a pool of black water with purple loose-strife fringing its banks and a few swan feathers scattered about on the grass. She never once shrieked from the cold but instead surfaced shouting incitements to those brave, amorous or drunk enough to follow her in. It looked inviting, always, with lily pads and flowers blooming among the reflections of the trees, but it was cold enough to make your bones ache and further along it became sinister and weedy as the blackthorns closed in. The nettled banks rose vertically and the barbed branches made it impossible to clamber up short of a mile or so downriver. She strode back through the golden stubble fields exultant, shaking water from her hair. There was always an obliging sunset and dear old Michael would usually play his harmonica. The tin bucket of hickory embers smoked the fish that they ate with soft brown bread and watercress. Julian can almost summon the taste just thinking about it.

His conscience has a dig at him as he pauses at the antiques shop door. "An incredible present," it repeats his words to him in a sneering voice. "Fancy not even making it home for her birthday," it says as he leans against the door to roll a skinny cigarette, doing the sums.

He imagines the gramophone resplendent on the grass beside the river: Billie Holiday or Patti Paige. How astonished Jena would be.

Crosby Stills and Nash on a more modern player floats from the flat above. Celestial harmonies soothe him; he feels almost peaceful for the first time in days, as he perfects his cigarette. He tilts his head to lick the paper and glances at an oil painting hanging on the back wall of the shop. A cormorant dries its wings against a background of emerald green but Julian's eye is instantly diverted to an ornate gilt mirror beside it. Lord above. His heart leaps, maybe he shouts out. Julia's face is reflected there.

It's only one stop until his station. Julia's steady gaze floats before him as he shakes himself from a dream of falling. He has to shuffle his way to the front four carriages, sideways on, with the mirror clasped to his belly, cursing himself aloud. Theirs is a short platform: of course it is stupid. The mirror is an awkward travelling companion and a tear has started in a corner of its wrapping. It's past midnight when he alights at the empty platform, bad tempered and cold from his short nap. Oh for fucks sake. Jena isn't there to meet him in her beat-up Landrover. Did she think he'd really meant it when he said he'd be happy to walk?

He hoists his bag on to his shoulder, speaks sternly to the mirror, and starts the trudge from the station. There's a mist rising from the river that meanders the length of the village, it may even be a fine drizzle, he can't decide, everything silver by moonlight and the hedges closing in. The sweet smell of silage and manure remind him he's home, a dog howls across the valley and is answered with a bark. Julian hauls the mirror beneath the partial shelter of his jacket. Would his mother even like it? She'd better! It's a bit fancy: "Rococo" Julia said. The paper tears a little more: sticking out at one corner the wing of an angel trying to escape.

Gulping: "I'll buy it," with not a thought for its price or fine provenance. Standing beside Julia, struggling not to reach out and touch the back of her head.

Her eyes in the mirror: pale irises ringed with dark blue, almost black, as though the colour seeped to the edges. "It's exactly right," he said and gulped again as she told him the price.

He snorts at the memory, does the maths. He'll certainly be raiding the sell-by-date food bins outside the Co-op before the next term is out, despite his decision to stay on and work the summer at the Crown.

"I think what I like best is that the angel's face shows such tender concern." She spoke in a near whisper, almost reverential, as they stood together before its gilded glory. Her dark hair looked so soft; she was wearing a long sundress with an African print that left her shoulders bare.

"The frame," she'd had to remind him. The gilded angel, whose dove-like wings formed one side of it, could have been the Hunchback of Notre Dame for all he cared.

"He looks a bit like Marlon Brando," she said. "Do you think?" And then she bit the side of her lip but kept her gaze steady as they continued staring straight at one another in the mirror.

He marches on clutching the ungrateful mirror like an unwilling dance partner on this star-less, and frankly not so balmy August night. He grips it with both hands, trying not to bump it with his knees, avoiding the ruts in the road that suggest he trip up and get himself seven years bad luck into the bargain.

"Fancy not making it home for her birthday. You promised." His conscience looms out of the mist and keeps pace beside him, sneering at the tawdry package. "Think that'll absolve you for ruining the whole day?" it says.

It was like kicking a puppy when he told her: "You can't be serious?" she said as he made his rehearsed excuse. A Sunday barbecue at the Crown, an extra shift. "I'll be sacked if I try to wriggle out of it," he'd lied and lied, with the cord of the phone around his neck, and across the shambled room Julia engulfed in his dressing gown, aquamarine eyes brimful. "I'm so sorry," she mouthed, clutching bunches of dressing gown to her front. He managed to end the call and then there was nothing he could do but scoop Julia into his arms and lay her on his bed.

There's a sudden screech and he imagines he can feel the breath of feathers on the back of his head. He hopes he's not mistaken now he sees the Landrover's lights bobbing towards him around the corner.

Jena cranks open the door, hops out, exclaiming about lateness and the length of his hair. He scoots round to the boot and finds the dog blankets to wrap around the mirror.

"Go away nosey, it's your present," he says batting her away as she tries to stroke his hair.

"I need to come clean about missing your birthday," he says as they start along the bumpy road home, the smell of the dogs all pervading. She didn't seem to have a clue, ever, his mother, about her own comfort. She tells him that it doesn't matter about her birthday, not at all, but he can't see her face in the dark. He tries to explain about Julia – but it all sounds too fanciful as he blurts it out while she drives. The hawk, her startling beauty, the luck of finding her again – who the devil would've thought it — and the way he feels every cell in his body yearning for her.

At Firdaws he drinks in the air: wet, warm earth and roses, honeysuckle, farmyards, cows as before, but up here he can smell fields of newly cut hay and fruit on the trees burnished by the summer he's missed.

He sighs, and gives in to his mother's hugs. "It's so lovely to be here," he says going round to the boot for the mirror. It's the river he can smell most of all. The earth and stones crunch beneath his feet and the lights through the curtains welcome him home. The terriers on skittering feet leap at him and nip at his pockets.

He decides to tell her everything as they settle in the kitchen, dogs still hysterical until he sends them to sulk by the Rayburn.

Julia was waiting for him to finish his shift at the Crown, sitting on the bonnet of her little Fiat using the light of a streetlamp to read her book. "And that," he nods to the package, "all wrapped up and waiting for me on the back seat." She'd promised to deliver it and there it was in layers of shiny red paper; she'd even fixed it with a bow. She was still wearing the sundress but had a blue shawl to cover her shoulders. When she jumped down from the car he found himself lifting the fingers of her left hand to his lips and kissing them, making a joke of his courtly behaviour and she smiled and bit her lip but didn't pull her hand away. He pressed her fingers to his face and he could smell the leather of the gauntlet and she laughed again when he told her, and said that yes she had flown the hawk.

"Oh, shush." Why won't she listen properly? His mother is drowning him out clattering about; filling the kettle, water from the tap thumping.

"Or would you prefer a gin?" She asks him.

He nods and when she's poured the gin and cracked the ice they clink glasses. He should have got the earlier train; his mother looks like it's well past her bedtime. He notices grey pouches at the corners of her mouth and her skin is like a paper bag that's been crumpled. The cat yawns rudely on the table between them, confident that neither of them would dream of shooing it off.

"So, who did you get to swim with you down the river?"

"Michael," she says and sloshes into their glasses another couple of fingers of gin.

Julian snorts. "You're lucky it didn't kill him."

"I am," she says.

The cat's purr is almost deafening as he scratches it under the chin. For a moment he finds it hard to keeping looking at her. She's thinner than before, a little deflated in her dress of worn-out looking daisies. He used to be able to see it when people said that he was her spitting image but not so much now that her bones have started showing through.

He can't decide what to tell her of that glorious night: leaping up the stairs to his digs, Julia behind him, heaping discarded clothing, scooping papers, books, socks from the sofa to make a space, wishing he had fresh milk in the fridge; through his curtainless window nothing more than the slimmest rib of a moon to judge them. In the morning she woke before he did and was already tiptoeing for the door. How quickly he'd sprung from the sheets to wrestle with her and pull down her sundress but she had pushed him away, covering herself, trying to tell him through her laughter: "No! I can't be late. I've got the hawk to see to before work."

She told him that the day-old chicks and the limp pink mice made her feel sick. "Defrosting, ugh" and he'd watched her wrinkle her adorable nose as she said: "To be honest I'd rather not have to deal with Lucifer and his disgusting diet at all but when my husband's away there isn't much choice but do it." And she'd blushed just as hotly as him when he couldn't make himself say whatever it was he was supposed to say next. After that nothing was ever more erotic than the smell of that gauntlet's oiled leather on her fingers.

His mother's disapproval is etched on her face and he has the sudden urge to giggle inanely. "She was leaving him, he was leaving her," he shrugs. "She told me it'd been going on so long she no longer knew which way around it was." He holds out the innocent palms of his hands but still she tuts at him and looks at the kitchen clock.

"It's getting awfully late," she says. "And there's something I really do have to tell you."

"Hey," he interrupts with strained gaiety. "You've still got to open your present tonight."

The parcel leans against a wall hectically Blu-tacked with Julian's drawings: from potato men sprouting arms and legs ("My Mummy"), to skyscrapers and towers and a not bad charcoal sketch of Raffael, their old alsatian, tattered but surviving. Besides his torn red package is a dresser, shelves heavily populated with clay animals – two by two – that they had brought into being throughout his childhood.

"It's your present." He slides it to Jena.

A terrier whines, stretches, and jumps into one of the stuffed chairs beside the Rayburn. He imagines Julia sitting there, her legs dangling over its arm. That day couldn't come soon enough. He smiles broadly to himself at the thought of showing Firdaws to Julia.

She's quite stern when she says: "Finish what you were saying first, then I need to tell you something" and so he props her present back against the wall and starts to pace. It's hard to find the words for what happened: Julia coming to him in the middle of the night, her shirt hanging from her in ribbons, bruises blooming across her back, a patch of bare scalp at the crown of her head from where that bastard had held her by her hair to thump her.

"I couldn't leave her," he said. "You do understand, don't you?"

"Stop pacing!" She orders him into his chair, grabs his hand and squeezes it hard across the table. He's finding that even simple eye contact has become a self-conscious act: "It was the night before your birthday …" he says. "I'm so sorry I wasn't here …"

"Will you stop apologising! I had a lovely day," she almost snaps at him but immediately looks downcast. He notices how sharply her clavicles stick out, and the tendons of her long skinny neck and then that her eyes are about to flood. She wipes them impatiently with her wrist, and blurts: "On my birthday Michael asked me to move in with him and I said that if he swam the river with me I would."

Julian feels his heart twist. Fat little Michael with his harmonica and his corduroy jeans. "Michael? And you're going to do that?"

She nods.

"Why now?"

"It's been a worry," she keeps getting up and sitting down again, unable to settle. He hates her tears and has to concentrate on the dogs, now sleeping curled Yin and Yang into the cushions of the chair.

"What will happen to Firdaws if you're not here all the time?" he asks. She thumps the table making him jump. "They've made me give up the lease on Firdaws." It comes out as a wail. She thumps it again and the cat leaps to the floor. "I never thought they'd go through with it," she says. "Firdaws was only in trust to me until you came of age."

It seems impossible when he leaves that he will never go back there. The library book lies unopened on the table and he rests his head against the black window of the train heading east. Had he always known that Firdaws would be taken from them? Jena said that he had and, out of nowhere, comes a memory of the first time he swam the river.

Pinkish clouds lent the surface a pearly sheen and in she went, a long, perfect arc straight to the heart of the river, the deepest part, but with no thought for Raffael the rescue alsatian who leapt in and swam out to save her.

"Oh my God! He's like a big brown bear." She swam with the dog gulping his way through the lily pads.

"Call him back!" she shouted. "He can't make it all the way down to where he'll be able to get out." And Michael slipping – and disappointing Julian that he didn't fall in – hauling Raffy out by his neck, waterlogged, yelping and snapping, his need to rescue his damsel entirely undiminished.

While Michael wrestled with the dog, Julian stayed at the edge of the riverbank, looking down at his mother among the lily pads. She held her arms out and without really thinking he jumped and half fell towards her and the icy knife shock of the water.

"Are you sure you'll make it all the way?" she asked as Julian gasped at the cold. "There's no way out and nowhere to put your feet down in between here and swan bank."

He was treading water, unsure, but she had already set off, carving long strokes through the water, Michael or one of the others shouting to him from the bank: "You'll freeze your bollocks off!"

She was a powerful swimmer: it was as though she parted the river before him. He was spooked when it became narrow – it was so eerily silent – and they swam through a tunnel of choking blackthorns and weeds with long tendrils and he started to swallow mouthfuls of water in his panic, and to cough. She told him to think of the insistent fingers winding around his scrawny arms and legs as "lovely massage" and reassured him that soon they would be clear of their slippery caresses and in another wide pool where he would be able to float on his back and rest.

It was a little deeper as they set off again and he'd asked her to slow down so that they could swim side by side as the weeds slithered by beneath them.

"That's it, we're clear of them now," she said, urging him on. "You know, the weeds are nothing to get in such a flap about. It's the snake that worries me more."

"Didn't I tell you?" she continued, timing her words to the rhythm of her stroke. "A couple of weeks ago I took Raffy for a walk to swan bank. I sat with him there for a while to watch the damsel flies dance. Oh look – like those two over there," she gestured across the reeds, but Julian could look nowhere but the water that surrounded him, darkness visible all around.

"Raffy was getting a drink at the edge when this enormous snake swam by. I could barely believe my eyes. It was as thick as my arm and so long it made three loops, like so," she demonstrated by undulating her arm, fingers making the shape of its head through the water. Julian cried out, and was rewarded with another mouthful of river, and she told him how she watched from the bank. "It gets worse," she said as he kicked his legs, splashing too much to get anywhere fast. "I was still staring at the snake when it doubled back and as it reached the dog it rose from the water and hissed straight in his face." She said she might have imagined that it had fangs. "Must've had young nearby, I suppose," she added as she swept ahead of him with her long stroke.

He was panting when they reached the bank; he couldn't haul himself up its muddy sides quick enough. They lay on the grass to catch their breath, he'd scraped himself getting out and there was a little blood spreading along his shin.

"Why did you tell me that about the snake?" he asked her. She sat up and touched his forehead with her palm, looking concerned, as though he might have a temperature. "I don't know, I suppose I was frightened," she said and she pulled him to his feet so that they could walk back to the others and the fire that she felt certain Michael would've lit on the river bank to keep them warm.

Photograph: Karen Robinson

• Polly Samson is the author of two collections of short stories, Lying in Bed (1999) and Perfect Lives (2011), and a novel Out of the Picture (2002). With her husband David Gilmour, she co-wrote many of the lyrics on Pink Floyd's The Division Bell and Gilmour's third solo album, On an Island